This invention relates to an expansion tank for the coolant of a coolant circulating system of an intenal-combustion engine having a filling chamber for receiving the coolant, an expansion chamber that is separated from it by means of a partition and a connecting line that connects an upper area of the filling chamber with a lower area of the expansion chamber.
A coolant expansion tank of this type is known from DE-OS 28 52 725. There the tank, by means of a vertically arranged partition, is divided into a filling chamber and an expansion chamber. The upper area of the filling chamber, via a line, is connected to the lower area of the expansion chamber. Normally, the filling chamber is filled with coolant up to a certain level. In the case of an extensive heating and thus an expansion of the volume of the coolant, this coolant, flows from the filling chamber, via the line, into the expansion chamber and when it is subsequently cooled, is drawn back into the filling chamber by means of a vacuum. From the underside of the filling chamber of the known tank, a line leads to a suction pump which transports the taken-in coolant back into the circulating system. By dividing the known tank into a filling chamber and an expansion chamber, in the case of a high cooling liquid level in the filling tank, the possibility of cavitation phenomena of the coolant in the line leading to the pump, and thus the possibiility of the occurrence of vapor bubbles because of the vacuum generated by the pump, is reduced. However, if the coolant level in the filling chamber, because of a loss of coolant, falls to a minimal level, the danger of cavitation phenomena in the line leading to the pump is increased because of the reduced geodetic level.
It is the objective of the invention to develop an expansion tank for the coolant of the initially mentioned type in such a way that in any operating condition, thus also in the case of a loss of coolant, damage of the components to be cooled is largely impossible. This objective is achieved by arranging the expansion chamber essentially below the filling chamber.
By means of this arrangement, even in the case of a coolant loss resulting in a lowering of the coolant level of the filling chamber, coolant still exists up to the level of the expansion chamber located under the filling chamber above the line leading to the pump and thus, because of the still relatively high geodetic level, cavitation phenomena in the pipe are reduced.
In the case of an advantageous development of the invention, the connecting line at the connecting point to the upper area of the filling chamber is developed into an air space, the highest point of which is located above the highest point of the filling chamber. In addition, it is possible to shape the connecting line at the connecting point to the lower area of the expansion chamber into a collecting space, the lowest point of which is located under the lowest point of the expansion chamber. By this measure, even when the filling chamber is completely filled with coolant, the air space is not filled with liquid and therefore a separation of gas from the coolant of the expansion chamber into this air space is possible. By means of the collecting space at the connecting point to the expansion chamber, all coolant from the expansion chamber can be sucked back into the filling chamber by means of a vacuum.
In the case of another advantageous development of the invention, a valve connection piece is located at the upper side of the tank that, by means of a duct, is connected with the expansion chamber and that can be closed by means of a valve cap having a pressure control valve. When the pressure in the expansion chamber rises above a certain value, the pressure control valve opens and discharges gas, to limit the pressure in the whole coolant circulating system.
An advantageous further development of the invention provides a suction connection piece that is located at the underside of the tank and that, via a connection, particularly an indentation developed by means of a slope, is connected to the filling chamber. By means of this suction connection piece, coolant is let off from the filling chamber.
It is especially advantageous to develop the partition between the filling chamber and the expansion chamber essentially horizontal. It is also advantageous to mount the connecting line at a tank wall. Because of these measures, it is possible, in the case of a vertical division of the whole tank into two shells, to produce these two parts by means of an injection process of plastic and to fit them together by means of corresponding connecting methods. The resulting division joint will then intersect the connecting line, making possible a simple shaping-out of this connecting line.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.